| 摘要 |
An amplifier circuit includes a first operational amplifier having an inverting input and a non-inverting input. The non-inverting input receives an input signal, and the inverting input is connected to a noise generating system. The amplifier circuit further includes a second operational amplifier having an inverting input and a non-inverting input. The non-inverting input of the second operational amplifier receives an input signal, and the inverting input is connected to a noise generating system. A differential in/out operational amplifier, in the amplifier circuit, has an inverting input connected to an output of the second operational amplifier and a non-inverting input connected to an output of the first operational amplifier. The noise generating system injects a narrow band noise into a differential amplifier with no insertion loss and mismatching along the signal path. The narrow band noise is obtained by amplifying thermal noise of an amplifier. The amplified thermal noise is bandwidth limited. The bandwidth limited amplified thermal noise is filtered by a low pass a filter.
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